Mutations in Drosophila rdgB cause light-enhanced retinal degeneration. A clone was obtained from a subtracted bovine retina pigment epithelium (RPE)/retina cDNA library which appears to code for a mammalian rdgB homolog (M-rdgB). The clone is 1.3 kb and shows 56% identity and 75% similarity with rdgB at the protein level. Reverse transcription-PCR (RT- PCR) with primers based on the bovine M-rdgB sequence indicate that M-rdgB is expressed specifically in retina and/or RPE and, to a lower level, in the brain. Understanding of the function of M-rdgB will likely provide new insight into vertebrate RPE/retina biology. This proposal will focus on characterization of the molecular aspects of this clone, determination of its spatial and developmental pattern of expression, and investigation of its possible functions. Since Drosophila rdgB is thought to be involved in the phototransduction pathway, the study of M-rdgB may yield new information about mammalian phototransduction. Since many mutations in the genes involved in the phototransduction pathway cause retinal degeneration, M-rdgB is a promising candidate gene that may be involved in human retinal degeneration.